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Explorer: S-30

Explorer 8 or S-30 was a 41 kg mercury-battery-powered, earth-orbiting satellite designed to
obtain measurements of the electron density, the electron temperature, the ion
concentration, the ion mass, the micrometeorite distribution, and the micrometeorite mass
in the ionosphere at altitudes between 400 and 1600 km. It was intended to study the
temporal and spatial distribution of these properties and their variation from full sunlit
conditions to full shadow, or nighttime, conditions.

The payload was in the form of two truncated cones with the bases attached to a
cylindrical equator. The outer shell was aluminum and had a diameter of 76 cm and a height
of 76 cm. The 108.00 MHz transmitter had 100 mW average power, and it functioned for the
life of the battery pack (54 days). The data system included telemetry consisting of
continuous operation with real-time transmission.

To avoid the possibility of effects on the experiments by asymmetrical charging on
solar cell surfaces, solar cells were not used.

Experiment instrumentation included:

an RF impedance probe,

an ion current monitor,

a retarding potential probe,

a two-element and

a three-element electron temperature probe,

an electron current monitor,

a photomultiplier-type and

a microphone-type micrometeorite detector,

an electric field meter,

a solar horizon sensor, and

thermistor temperature probes.

Simultaneous measurements of electron and ion concentration were used to resolve the
question of neutrality of the medium.

Battery power failed on 27 December 1960. Considerable difficulty was encountered with
decommutating the telemetered data to make machine processing possible. As a result of
these difficulties, the data were mostly processed by hand. In spite of these
difficulties, considerable new knowledge about the ionosphere was gained from operation of
the satellite.